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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 19:33:14 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 19:33:14 +0000 |
commit | 36d22d82aa202bb199967e9512281e9a53db42c9 (patch) | |
tree | 105e8c98ddea1c1e4784a60a5a6410fa416be2de /third_party/python/ply/example/unicalc/calc.py | |
parent | Initial commit. (diff) | |
download | firefox-esr-upstream.tar.xz firefox-esr-upstream.zip |
Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'third_party/python/ply/example/unicalc/calc.py')
-rw-r--r-- | third_party/python/ply/example/unicalc/calc.py | 133 |
1 files changed, 133 insertions, 0 deletions
diff --git a/third_party/python/ply/example/unicalc/calc.py b/third_party/python/ply/example/unicalc/calc.py new file mode 100644 index 0000000000..901c4b9d76 --- /dev/null +++ b/third_party/python/ply/example/unicalc/calc.py @@ -0,0 +1,133 @@ +# ----------------------------------------------------------------------------- +# calc.py +# +# A simple calculator with variables. This is from O'Reilly's +# "Lex and Yacc", p. 63. +# +# This example uses unicode strings for tokens, docstrings, and input. +# ----------------------------------------------------------------------------- + +import sys +sys.path.insert(0, "../..") + +tokens = ( + 'NAME', 'NUMBER', + 'PLUS', 'MINUS', 'TIMES', 'DIVIDE', 'EQUALS', + 'LPAREN', 'RPAREN', +) + +# Tokens + +t_PLUS = ur'\+' +t_MINUS = ur'-' +t_TIMES = ur'\*' +t_DIVIDE = ur'/' +t_EQUALS = ur'=' +t_LPAREN = ur'\(' +t_RPAREN = ur'\)' +t_NAME = ur'[a-zA-Z_][a-zA-Z0-9_]*' + + +def t_NUMBER(t): + ur'\d+' + try: + t.value = int(t.value) + except ValueError: + print "Integer value too large", t.value + t.value = 0 + return t + +t_ignore = u" \t" + + +def t_newline(t): + ur'\n+' + t.lexer.lineno += t.value.count("\n") + + +def t_error(t): + print "Illegal character '%s'" % t.value[0] + t.lexer.skip(1) + +# Build the lexer +import ply.lex as lex +lex.lex() + +# Parsing rules + +precedence = ( + ('left', 'PLUS', 'MINUS'), + ('left', 'TIMES', 'DIVIDE'), + ('right', 'UMINUS'), +) + +# dictionary of names +names = {} + + +def p_statement_assign(p): + 'statement : NAME EQUALS expression' + names[p[1]] = p[3] + + +def p_statement_expr(p): + 'statement : expression' + print p[1] + + +def p_expression_binop(p): + '''expression : expression PLUS expression + | expression MINUS expression + | expression TIMES expression + | expression DIVIDE expression''' + if p[2] == u'+': + p[0] = p[1] + p[3] + elif p[2] == u'-': + p[0] = p[1] - p[3] + elif p[2] == u'*': + p[0] = p[1] * p[3] + elif p[2] == u'/': + p[0] = p[1] / p[3] + + +def p_expression_uminus(p): + 'expression : MINUS expression %prec UMINUS' + p[0] = -p[2] + + +def p_expression_group(p): + 'expression : LPAREN expression RPAREN' + p[0] = p[2] + + +def p_expression_number(p): + 'expression : NUMBER' + p[0] = p[1] + + +def p_expression_name(p): + 'expression : NAME' + try: + p[0] = names[p[1]] + except LookupError: + print "Undefined name '%s'" % p[1] + p[0] = 0 + + +def p_error(p): + if p: + print "Syntax error at '%s'" % p.value + else: + print "Syntax error at EOF" + +import ply.yacc as yacc +yacc.yacc() + +while 1: + try: + s = raw_input('calc > ') + except EOFError: + break + if not s: + continue + yacc.parse(unicode(s)) |